docs: def __combine_windows(w1, w2):
      """
      Joins two windows (defined by tuple of slices) such that their maximum
      combined extend is covered by the new returned window.
      """
      res = []
      for s1, s2 in zip(w1, w2):
          res.append(slice(min(s1.start, s2.start), max(s1.stop, s2.stop)))
      return tuple(res)